Help with melting EGI fuse
02-25-09, 01:57 AM
#1
Rotary No Ka Oi
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Help with melting EGI fuse
Well I find that after a minute or two my EGI fuse gets hot...I mean scalding hot. It will melt the fuse and the car will just die. Needless to say I haven't driven it in a while. I am by no means an electrician so this is frustrating. I do know that the previous owner installed 720's in the secondaries and is running resistors inline...I have a feeling this may be the culprit but thought I would throw it out there. Any advice would be great.
02-25-09, 05:49 PM
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Check the wiring,It sounds like the Resistors are Not capable of Dissipating heat,and maybe they are the wrong wattage.If they are not the Right Wattage,then I could see your EGI fuse taking the "brunt" of the Current" which it should do.
I'd be checking the engine wiring.The EGI Fuse also incorporates the Emissions equipment.,senders Etc,so Really any Bare wires,or touching wires will cause the EGI fuse to Come into play(Pop).
I'd be checking the engine wiring.The EGI Fuse also incorporates the Emissions equipment.,senders Etc,so Really any Bare wires,or touching wires will cause the EGI fuse to Come into play(Pop).
02-25-09, 10:14 PM
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No no no no no!!! The resistors prevent the ecu from seeing too much current and have no effect on the draw. There is no reason thoes injectors or the resistors would be the cause of melting a fuse like that. If they were for whatever reason drawing too much current, than the fuse would blow not melt. If the resistors were wrong, you would get melting around the resistor, not the fuse.
Chances are, there was a bad connection either between a fuse and the fuse block, or the plug out and the fuse block. This caused resistance that shouldn't have been there but kept the current below the rating of the fuse. Chances are you have melted either your fuse block and/or some of the surrounding wires/plugs. You will need to replace whatever has been dammaged by the heat. Start by pulling the whole fuse block off the car and inspecting to see where it is dammaged, and replace items as needed. DO NOT reuse melted items since they will likely cause the same issue in the future if reused.
Chances are, there was a bad connection either between a fuse and the fuse block, or the plug out and the fuse block. This caused resistance that shouldn't have been there but kept the current below the rating of the fuse. Chances are you have melted either your fuse block and/or some of the surrounding wires/plugs. You will need to replace whatever has been dammaged by the heat. Start by pulling the whole fuse block off the car and inspecting to see where it is dammaged, and replace items as needed. DO NOT reuse melted items since they will likely cause the same issue in the future if reused.
02-25-09, 11:06 PM
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No no no no no!!! (1)The resistors prevent the ecu from seeing too much current and (2)have no effect on the draw. There is no reason those injectors or the resistors would be the cause of melting a fuse like that. If they were for whatever reason drawing too much current, than the fuse would blow not melt. (3)If the resistors were wrong, you would get melting around the resistor, not the fuse.
Chances are, there was a bad connection either between a fuse and the fuse block, or the plug out and the fuse block. (4)This caused resistance that shouldn't have been there but kept the current below the rating of the fuse. Chances are you have melted either your fuse block and/or some of the surrounding wires/plugs. You will need to replace whatever has been dammaged by the heat. Start by pulling the whole fuse block off the car and inspecting to see where it is dammaged, and replace items as needed. DO NOT reuse melted items since they will likely cause the same issue in the future if reused.
Chances are, there was a bad connection either between a fuse and the fuse block, or the plug out and the fuse block. (4)This caused resistance that shouldn't have been there but kept the current below the rating of the fuse. Chances are you have melted either your fuse block and/or some of the surrounding wires/plugs. You will need to replace whatever has been dammaged by the heat. Start by pulling the whole fuse block off the car and inspecting to see where it is dammaged, and replace items as needed. DO NOT reuse melted items since they will likely cause the same issue in the future if reused.
You are wrong on almost everything you say.
I = V/R.
Ohms law. study it like mad. and dont pretend to know about electrical systems.
(1) Incorrect. The resistors reduce the LOAD. since the ECU is the thing actually putting out the current.
Ever short anything in your car? the resistance is very low when you short things out. The only difference between a short, and operating something like an injector is resistance induced by the equipment. Lights are a great simple example of a simple resistor that lets out the current via heat and light.
(2) Once again, this is incorrect.
A little reminder. I = V/R
Current is equal to voltage divided by resistance.
The lower the resistance, the more current is flowed through a circuit.
(3)Incorrect as well. Less resistance, more flow. Excessive flow, blown fuse. While yes, if an incorrect resistor is used, they CAN get hot, but the fact you point directly to the resistor is incorrect.
(4)Added resistance lowers current, not increases.
Don't take this personally, but more as being more educated on the subject.
To the OP. check and see if any of the other wires in the EGI system are warm. How long does it take for this symptom to occur?
02-26-09, 02:49 AM
#5
Rotary No Ka Oi
Thread Starter
Thanks for the resonses guys.
Well the car ran this setup fine for years so its not like its anything new has been added. It only takes a matter of minutes to be to hot to even touch. The connector of wires the snaps under the fusebox to the egi fuse is also melted. I know these things are next to impossible to diagnose on the net so I appretiate the effort!
Well the car ran this setup fine for years so its not like its anything new has been added. It only takes a matter of minutes to be to hot to even touch. The connector of wires the snaps under the fusebox to the egi fuse is also melted. I know these things are next to impossible to diagnose on the net so I appretiate the effort!
02-26-09, 10:35 AM
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when the previous owner rewired them, did he use proper gauge wire/connectors? or just what he had on hand??
The fuse could be getting hot via heat conduction from the wires. not necessarily the fuse itself getting warm.
The fuse could be getting hot via heat conduction from the wires. not necessarily the fuse itself getting warm.
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02-26-09, 05:07 PM
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You are wrong on almost everything you say.
I = V/R.
Ohms law. study it like mad. and dont pretend to know about electrical systems.
(1) Incorrect. The resistors reduce the LOAD. since the ECU is the thing actually putting out the current.
Ever short anything in your car? the resistance is very low when you short things out. The only difference between a short, and operating something like an injector is resistance induced by the equipment. Lights are a great simple example of a simple resistor that lets out the current via heat and light.
I am refering to the trigger, not the feed. The feed is a constant and could be sourced off anything that has 12v on the IGN 1 circut in the car. My apologies, I should have refered to the flyback circutry
(2) Once again, this is incorrect.
A little reminder. I = V/R
Current is equal to voltage divided by resistance.
The lower the resistance, the more current is flowed through a circuit.
Your assuming that an ECU would run a low z injector the same way it run's a high z injector, which it does not. Resistors, in this case, allow the ECU to run the low z injector as if it was a high z. Either way, without doing the math, the difference in draw of a high z vs. low z vs. low z w/ resistors is going to be virtually identical, and negligable for a 40amp fuse.
(3)Incorrect as well. Less resistance, more flow. Excessive flow, blown fuse. While yes, if an incorrect resistor is used, they CAN get hot, but the fact you point directly to the resistor is incorrect.
Yes, if the resistor was insufficient you could get melting around it, but I forgot to mention that the other thing that could happen is you would blow some of the circutry in your ECU. See below where I will explain pulse width modulation
(4)Added resistance lowers current, not increases.
Yes... I didn't say it raised current. The resistance provides the heat to melt the fuse, and the lack of sufficent current to blow the fuse prevented it from blowing. Read before you say I'm wrong.
Don't take this personally, but more as being more educated on the subject.
To the OP. check and see if any of the other wires in the EGI system are warm. How long does it take for this symptom to occur?
I = V/R.
Ohms law. study it like mad. and dont pretend to know about electrical systems.
(1) Incorrect. The resistors reduce the LOAD. since the ECU is the thing actually putting out the current.
Ever short anything in your car? the resistance is very low when you short things out. The only difference between a short, and operating something like an injector is resistance induced by the equipment. Lights are a great simple example of a simple resistor that lets out the current via heat and light.
I am refering to the trigger, not the feed. The feed is a constant and could be sourced off anything that has 12v on the IGN 1 circut in the car. My apologies, I should have refered to the flyback circutry
(2) Once again, this is incorrect.
A little reminder. I = V/R
Current is equal to voltage divided by resistance.
The lower the resistance, the more current is flowed through a circuit.
Your assuming that an ECU would run a low z injector the same way it run's a high z injector, which it does not. Resistors, in this case, allow the ECU to run the low z injector as if it was a high z. Either way, without doing the math, the difference in draw of a high z vs. low z vs. low z w/ resistors is going to be virtually identical, and negligable for a 40amp fuse.
(3)Incorrect as well. Less resistance, more flow. Excessive flow, blown fuse. While yes, if an incorrect resistor is used, they CAN get hot, but the fact you point directly to the resistor is incorrect.
Yes, if the resistor was insufficient you could get melting around it, but I forgot to mention that the other thing that could happen is you would blow some of the circutry in your ECU. See below where I will explain pulse width modulation
(4)Added resistance lowers current, not increases.
Yes... I didn't say it raised current. The resistance provides the heat to melt the fuse, and the lack of sufficent current to blow the fuse prevented it from blowing. Read before you say I'm wrong.
Don't take this personally, but more as being more educated on the subject.
To the OP. check and see if any of the other wires in the EGI system are warm. How long does it take for this symptom to occur?
Let's talk about low impedence (peak and hold) injectors versus high impedence. High z injectors allow an ecu to apply voltage and simple hold it untill enough time has elasped to release the fuel. If you were to do this with a low z injector then too much, let's use power, will be seen on the trigger circut in the ECU and it will overheat, causing traces to blow and other components to possibly melt. Even if this happened, the only reason it would put more load on the fuse is if something shorted out when it overheated and stayed shorted. If that was to happen, it would blow the fuse before melting it.
To run a Low z injector without putting a resistor in line, the ECU needs to be capeable of PWM. This means that it applies voltage (and current) to the injector for its opening time, and then once it is open it pulses, thus limiting voltage and current seen by the injector and the flyback on the ECU. This prevents the injector and other componentry from being dammaged. Resistors in line with the injectors makes an ECU which is incapeable of running PWM able to fire a low z injector with dammage to the injector or itself. Either way, the wrong resistor would potentially cause dammage to itself, the injector, and the ECU only... not the fuse block which is many feet away.
So, let's summerize. The resistors are not causing the fuse to melt. The source of heat will be more localized. Could there be an issue with the resistors? Sure, cause it sounds like their installation is a bit sketchy. But the OP can trace back as much wireing around the resistors as he wants and it still won't fix the problem he asked about.
Craig
02-27-09, 06:02 AM
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For some reason Profile does not work for me anymore. I see no car there. Matters not I guess.
EGI fuse feeds the coils, injectors, ECU and all the solenoids (approx 9) on the vacuum rack , the check connector for the TPS and the diagnostic connector,plus the solenoids on the ACV and the alternator S wire and Air Bag system on some cars. And feeds the OMP stepping motor.
Soooooooo......why wouldn't the problem be in those areas?
IF the EGI fuse gets hot just by the key being on, you could cut your trouble shooting in half by depinning one of the two wires that go from the EGI fuse to the Main Relay, and seeing if the fuse cools off or does not get hot when that particular wire is disconnected. That'd give you a hint as to which path to follow.
More likely than not he removed the solenoids/ACV and has a wire of one of the solenoids shorted to gnd.
EGI fuse feeds the coils, injectors, ECU and all the solenoids (approx 9) on the vacuum rack , the check connector for the TPS and the diagnostic connector,plus the solenoids on the ACV and the alternator S wire and Air Bag system on some cars. And feeds the OMP stepping motor.
Soooooooo......why wouldn't the problem be in those areas?
IF the EGI fuse gets hot just by the key being on, you could cut your trouble shooting in half by depinning one of the two wires that go from the EGI fuse to the Main Relay, and seeing if the fuse cools off or does not get hot when that particular wire is disconnected. That'd give you a hint as to which path to follow.
More likely than not he removed the solenoids/ACV and has a wire of one of the solenoids shorted to gnd.
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